As is known, a groove is called rolling (or open) when its joints are parallel to the longitudinal axis of the rolls or when the angle formed by the joints and the longitudinal axis of the rolls is less than 60.degree.. The passage of a bar in a groove is called a pass when a rolling action is exerted on the bar via all or part of the groove contour. In the present application, a groove will be called specific when its contours and dimensions are well adapted to the pass which is made therein.
To arrange side by side, separately, in conventional rolling, similar or different specific grooves on the rolls of two-high or three-high stands, belongs to the state of the art of rolling since the 18th century.
It is known, for reversing two-high edger stands of a universal beam rolling mill, to vary the dimensions of a single groove in a vertical direction by raising or screwdown of the rolls, that is to say by varying the spacing of the rolls. This method is disclosed, among others, for the rolling of beams, by U.S. Pat. No. 1,812,246 dated June, 30, 1931.
It is known from French Pat. No. 1,298,605, dated Aug. 3, 1961 and relating to a reversing two-high edger stand of a universal beam rolling mill, to use a technique consisting of shifting the edger rolls perpendicularly to the rolling line, to bring in turn into the rolling line at least two separate specific edging grooves, similar or different, said grooves (known per se) being arranged side by side on the rolls.
From French Pat. No. 1,447,939, corresponding to U.S. Pat. No. 3,342,053, dated June 27, 1966 is known a process for universal rolling of rails, in which the rail is rolled in universal stands and two-high edger stands. In this process the edging passes are carried out in reversible or non-reversible stands comprising a single groove. In the reversing edger stands, the dimensions of the single groove are modified in the vertical direction by raising or screw-down of the rolls. In the non-reversing edger stands each groove is specific.
Also known from French Pat. No. 69.42489 dated Dec. 9, 1969 published under No. 2.025.705, corresponding to U.S. Pat. No. 3,657,912, is the application to edging passes of universal rolled rails, of the technique revealed in French Pat. 1.298.605, corresponding to U.S. Pat. No. 3,165,948, for the edging of universal rolled beams, namely the shifting, during rolling of a rail, of the edging stand perpendicularly to the rolling line in order to bring in turn into the rolling line at least two specific edging grooves, either similar or different, arranged on the rolls (known per se) side by side and separated.
To arrange a plurality of grooves side by side but separated, according to the known state of the art, needs rolls of barrel length necessarily greater than the sum of the widths of the grooves. Such a length of barrel involves the rolls being heavy and therefore relatively costly. In the case of rolling mills whose stands are arranged as close as possible behind each other on the same roller table (line), for obvious economic reasons, the only known means for bringing a rail, for example, into the proper specific edging groove without causing detrimental damage to the same, consists of shifting the edger stand or its rolls perpendicularly to the rolling line. The extent of and the speed necessary for this displacement make such a stand costly to purchase, install and operate. Its intricacy also makes it more prone to breakdown.